This invention relates to the field of treating webs of material with pressure rolls, and more particularly to the field of improved pressure roll apparatus.
Many industries require the treatment of material webs with roller apparatus, for sizing, smoothing and similar operations. The paper and textile industries furnish two prominent examples in which such rollers are employed for a variety of tasks, with a roll usually opposed to another roll and the material passing through the nip between the rolls.
A widely used roll apparatus is the so-called "swimming" roll, in which a pressure roll, generally in the form of a hollow cylinder, is carried on a support extending concentrically through the pressure roll, with hydraulic fluid introduced into the gap between the two elements, resiliently supporting the pressure roll during operation. Usually, the space between the pressure roll and its support is subdivided into at least two chambers by longitudinal seals, carried on the support and bearing against the inner surface of the pressure roll, as described in Federal Republic of Germany Pat. No. 1,026,609. Although that reference describes an arrangement whereby the seals are placed 180 degrees apart, other arrangements are possible. For example, Federal Republic of Germany Auslegeschrift No. 2,461,914 teaches a placement in which the longitudinal seals are arranged to form two unequal chambers, the smaller of which is located in the area of the nip.
A major difficulty with swimming rolls has been the power loss occasioned by turbulence in the hydraulic fluid, as explained in detail hereafter. The present invention solves that problem, and thus it offers an improved and more efficient roll system.